1. Field of the Invention
The invention relates generally to processes and apparatus for removing dioxane components from materials such as solutions, dispersions, slurries, emulsions, and pastes. More particularly, the invention relates to processes that can remove 1,4-dioxane from alkoxylated fatty alcohol sulfate pastes to a level previously not possible.
2. Description of Related Technology
Detergent products contain surface active ingredients (sometimes referred to as “detergent active ingredients” or “detergent actives”), which may be neutralized salts of acids produced, for example, by sulfating or sulfonating C8-C20 organic materials and, preferably, C11-C18 organic materials, such as, for example, fatty alcohols, alkoxylated fatty alcohols, ethoxylated fatty alcohols, alkyl benzenes, alpha olefins, methyl esters, alkyl phenol alkoxylates, and alkyl phenol ethoxylates. The process of making detergent actives from the acid form is typically performed in a solvent, such as water and/or alcohol. The resulting detergent material may be a paste, a solution, or a slurry of various components. (The term detergent “paste” as used hereinafter is meant to include detergent solutions, slurries and pastes). Final detergent products are made from such detergent pastes.
Fatty alcohol ethoxy sulfates (AES) is a mild surfactant that generates considerable foam and has excellent degreasing properties. It is used in personal care products, such as shampoo, and liquid dish cleaners, for example. Since it is derived from fatty alcohol it can be made from natural oils, for example coconut oil.
1,4-dioxane is a by-product formed during the sulfation process of making fatty alcohol alkoxy sulfates and AES in relatively small amounts and that remains in the sulfated product. Consumer protection groups have become concerned about 1,4-dioxane in products including baby shampoo, for example. The U.S. Environmental Protection Agency classifies dioxane as a probable human carcinogen, and in California it is “classified to cause cancer” and has come under increasing scrutiny by consumer groups and regulatory bodies. Presently, there are no regulatory limits on the amount of 1,4-dioxane that is safe in these products; but some companies have started implementing their own quality standards. There is thus a need for minimizing 1,4-dioxane in sulfated products.
Technology for minimizing 1,4-dioxane formation has been reported in the literature dating back decades. Prior studies report steps that can be taken in the sulfation process to minimize the amount of 1,4-dioxane that forms. Reducing the SO3 gas concentration from 4% to 2.5%, for example, has a dramatic effect and cuts the amount of 1,4-dioxane that forms in half. Less dramatic benefits come from running at low mole ratios of SO3:feed so that conversion of the feed to the sulfated product is less complete. These changes have a dramatic impact on the production capacity and cost-efficiency of a sulfation plant. Moves such as these cut the plant capacity by as much as 50%.